Technologies providing reality to make a user feel a sense of realism in a virtual space are collectively called “TI (Tangible Interface)”, and a new concept of space including the user, virtual reality and a real world is called “tangible space”.
To realize the tangible space, it is first of all important to project and reflect a real life space thereon. Meanwhile, in order to allow the user to feel realism in a cyberspace implemented by a computer, stimuli for various senses need to be simultaneously provided. That is, complex senses, such as vision, touch, hearing, and the like need to be fused and provided to the user. Since a human usually recognizes objects and environments through the sense of sight, information obtained by a visual sensor is one of important information in profiling and recognizing an object.
3-dimensional data for an unknown object is restored by using the information obtained by the visual sensor and provided to the virtual space, thereby constructing the virtual space, but it is not sufficient for the user to accurately recognize the unknown object. For example, at a dark place or in a poorly lighted environment, it is impossible to accurately recognize the object with the visual sensor. Further, the rear side of the object out of vision cannot be recognized until an additional camera is provided at the rear side of the object or until special radar capable of detecting the rear side of the object is employed. Furthermore, it is difficult to recognize the texture or partial profile of the object surface through the vision.
To realize an accurate tangible space technology, it is important to develop a technology which realizes the stimuli and behaviors of the user on the basis of information about the sense of touch in the real world as well as the visual information. In particular, as a pre-requisite to realize the tangible space, development of a tactile sensor capable of providing tangible information by detecting the texture or partial profile of the object in the real world is demanded.
Conventionally, the measurement of the texture (i.e., surface roughness) of the object is performed only based on the visual information on the object surface obtained by optical cameras, which results in deterioration in accuracy. Alternatively, there is also suggested a method in which a laser is irradiated onto the object surface and information of the object surface is measured on the basis of reflected information from the object. According to this method, however, sufficient accuracy in measuring the surface texture of the object cannot be achieved.
Meanwhile, many tactile sensors have been developed to provide the tactile information of the object surface, but they have not been widely used in view of cost, reliability, and structural complexity. Further, studies using the conventional tactile sensors have been concentrated on the implementation of static recognition of the object profile. Therefore, though the contact position or contact force of the object can be expressed by using the conventional tactical sensors, dynamic changes according to the surface roughness, i.e., texture, cannot be sufficiently expressed.